Conventionally, polyhydroxystyrenes or derivatives thereof in which the hydroxyl groups are protected with an acid dissociable, dissolution inhibiting group, which display high transparency relative to a KrF excimer laser (248 nm), have been used as the resin component of chemically amplified resists.
However, these days, the miniaturization of semiconductor elements has progressed even further, and the development of processes using ArF excimer lasers (193 nm) is being vigorously pursued.
For processes using an ArF excimer laser as the light source, resins comprising a benzene ring such as polyhydroxystyrene have insufficient transparency relative to the ArF excimer laser (193 nm), and are consequently unsuitable for use in such processes.
Accordingly, in order to resolve this problem, resins containing no benzene rings, but comprising a unit within the principal chain derived from an acrylate ester or a methacrylate ester with a polycyclic hydrocarbon group such as an adamantane skeleton provided at the ester section, thereby offering excellent dry etching resistance, are attracting considerable interest, and many materials have already been proposed (Japanese Patent (Granted) Publication No. 2881969, Japanese Unexamined Patent Application, First Publication No. Hei 5-346668, Japanese Unexamined Patent Application, First Publication No. Hei 7-234511, Japanese Unexamined Patent Application, First Publication No. Hei 9-73173, Japanese Unexamined Patent Application, First Publication No. Hei 9-90637, Japanese Unexamined Patent Application, First Publication No. Hei 10-161313, Japanese Unexamined Patent Application, First Publication No. Hei 10-319595 and Japanese Unexamined Patent Application, First Publication No. Hei 11-12326).
However, in recent years the design rules required in semiconductor element production continue to become more stringent, and resolutions in the vicinity of 150 nm or 100 nm are necessary, and further improvements in resolution are keenly sought.
Furthermore, in addition to these types of improvements in resolution, in the formation processes for resist patterns in which the ratio between the size of the resist line sections relative to the size of the space sections is less than 1, the formation of so-called isolated resist patterns, in which, for example, the ratio of the size of the resist line sections relative to the size of the space sections is 1/9, are now also becoming increasingly necessary.
However, with conventional resists a problem arises in that the depth of focus range of this type of isolated resist pattern is unsatisfactory, and improvements are desirable.
Furthermore, in a pattern formation process in which isolated resist pattern sections of the type described above (sparse pattern sections) and pattern sections in which the line and space ratio is 1:1 (dense pattern sections) are mixed, a difference develops in the resist pattern size between the sparse pattern sections and the dense pattern sections, producing a so-called proximity effect problem, and in conventional resists, suppressing this type of proximity effect is difficult, and consequently improvements in this area are also keenly sought.